1. Field of the Invention
The present invention relates to a heat discharger, and, in particular, to a heat discharger suitable for application in heat pipes intended for artificial space satellites.
2. Description of the Related Art
Most space satellites in earth orbit are provided with a network of heat pipes for conducting heat. Such a network of heat pipes is provided so that the heat locally generated or accumulated, such as absorbed radiant heat from the sun, in one section of the satellite can be conducted through the heat pipes to sections in which heat is not accumulated. Heat sinks for discharging heat are provided for the heat pipes so that the heat conducted via the heat pipes can be radiated away via the heat sinks. The heat pipe and heat sink are integrally formed by extrusion so that the heat from the heat pipe is efficiently conducted to the heat sink.
There has, however, been a tendency for the amount of heat generated by installed electronic equipment to increase as a result of increases in size and complexity of satellites, creating a need to increase the size of the heat sink as a countermeasure against the increased amount of generated heat.
However, when the heat sink and heat pipe are integrally formed through extrusion of aluminum, as shown in FIG. 20, if the thickness T1 of the heat sink is equal to or greater than 2.5 times the wall thickness T2 of the heat pipe, the material flows towards the heat sink (shown by an arrow a in FIG. 20) because of the degree of flow of aluminum. Therefore, there had been a problem in that sections corresponding to the heat pipe could not be formed.
To this end, separately forming the heat sink and heat pipe and then welding them together has been proposed in consideration of the heat conduction efficiency. However, because, in order to reduce weight, heat pipe is primarily made of aluminum, application of heat generates strain, making welded aluminum pipe unsuitable for equipment for use in outer space, which requires extremely high precision in assembly.